Investments, Available-for-Sale Securities in Gross Unrealized Loss Position (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Fixed Maturity Securities [Member]
Estimated Fair Value [Abstract]
Less than 12 months	$ 10,066	$ 2,148
12 months or longer	87	272
Total	10,153	2,420
Gross Unrealized Losses [Abstract]
Less than 12 months	1,099	31
12 months or longer	18	14
Total	1,117	45
Corporate and Other Bonds [Member]
Estimated Fair Value [Abstract]
Less than 12 months	7,036	914
12 months or longer	44	186
Total	7,080	1,100
Gross Unrealized Losses [Abstract]
Less than 12 months	804	21
12 months or longer	13	11
Total	817	32
States, Municipalities and Political Subdivisions [Member]
Estimated Fair Value [Abstract]
Less than 12 months	82	34
Total	82	34
Gross Unrealized Losses [Abstract]
Less than 12 months	2
Total	2
Total Asset-Backed [Member]
Estimated Fair Value [Abstract]
Less than 12 months	2,861	1,079
12 months or longer	43	83
Total	2,904	1,162
Gross Unrealized Losses [Abstract]
Less than 12 months	289	7
12 months or longer	5	3
Total	294	10
Residential Mortgage-Backed [Member]
Estimated Fair Value [Abstract]
Less than 12 months	166	249
12 months or longer	22	30
Total	188	279
Gross Unrealized Losses [Abstract]
Less than 12 months	7	1
12 months or longer	1
Total	8	1
Commercial Mortgage-Backed [Member]
Estimated Fair Value [Abstract]
Less than 12 months	1,185	381
12 months or longer	12	20
Total	1,197	401
Gross Unrealized Losses [Abstract]
Less than 12 months	151	3
12 months or longer	2	2
Total	153	5
Other Asset-Backed [Member]
Estimated Fair Value [Abstract]
Less than 12 months	1,510	449
12 months or longer	9	33
Total	1,519	482
Gross Unrealized Losses [Abstract]
Less than 12 months	131	3
12 months or longer	2	1
Total	133	4
U.S. Treasury and Obligations of Government-sponsored Enterprises [Member]
Estimated Fair Value [Abstract]
Less than 12 months	2	62
12 months or longer		2
Total	2	64
Gross Unrealized Losses [Abstract]
Less than 12 months		2
Total		2
Foreign Government [Member]
Estimated Fair Value [Abstract]
Less than 12 months	76	59
12 months or longer		1
Total	76	60
Gross Unrealized Losses [Abstract]
Less than 12 months	4	1
Total	4	$ 1
Redeemable Preferred Stock [Member]
Estimated Fair Value [Abstract]
Less than 12 months	9
Total	$ 9